西非被动大陆边缘重力滑脱构造发育演化及成因机制

西非被动大陆边缘盆地在晚侏罗世伴随大西洋的裂开而形成,陆内裂陷构造旋回(晚侏罗世-早白垩世阿普特期(Aptian))主要发育陆内裂陷构造;过渡期构造旋回(阿普特期)沉积了一套潟湖相塑性层(盐岩);被动大陆边缘构造旋回(早白垩世阿尔布期(Albian)至今)共发育了两期重力滑脱构造,早白垩世阿尔布期-渐新世发育一期(早期)重力滑脱构造,中新世至今发育了另一期(晚期)重力滑脱构造。西非被动大陆边缘同一期重力滑脱构造具有从早到晚由陆向海的前展式发育规律,且多期重力滑脱构造具有从早到晚由陆向海迁移的进积叠加规律。西非被动大陆边缘重力滑脱构造发育的主要控制因素是大地构造背景、地层掀斜、滑脱面形态,其中大地构造背景控制重力滑脱构造体系类型,地层掀斜是引起地质体重力滑脱和变形的根本、控制构造变形的强度,滑脱面形态控制着重力滑脱构造类型和发育位置;次要控制因素是差异重力负载和塑性滑脱层等。并在此基础上建立了宽缓型凹面斜坡和窄陡型斜坡滑脱面下的西非被动大陆边缘重力滑脱构造成因发育模式。     

安徽青阳地区早古生代地层的韧性变形及形成机制

安徽省青阳地区早古生代地层普遍发生了较强烈的韧性变形，主要变形形迹有：滑脱断层、顺层劈理、小型韧性剪切带、流变褶皱、石香肠等，显微构造分析也显示岩石的韧性变形、强烈的构造置换作用．岩石的构造变形达中－下部构造层次上部，其形成机制为重力滑覆成因．     

歧口凹陷滑脱构造剖析及对油气地质意义

重力滑脱构造在盆地演化中较为常见,地层或岩体在重力作用下向下方滑动所产生的构造变动存在广泛。歧口凹陷为渤海湾新生代盆地内一个次级构造单元凹陷,其特点是新生代沉积巨厚且构造活动强烈,为重力滑脱和相关构造形成提供了发育条件。按照滑脱面性质的不同,将歧口凹陷的滑脱构造分为3类:地层-断裂复合滑脱、顺层滑脱和断裂滑脱。在该凹陷中选其各自具代表性的构造,如埕北滑脱构造、塘沽新港滑脱构造和大张坨滑脱构造进行结构特征和演化等方面剖析。研究认为,歧口凹陷滑脱构造形成的主控因素为新生代凹陷区快速沉积、凸起带强烈隆升、前第三纪地层的滑移层和热力作用。滑脱构造大多有褶皱和断裂相伴生,其组合方式不同可为油气成藏提供有利条件。     

尼日尔三角洲的重力滑动构造

位于南大西洋东岸被动大陆边缘之上的尼日尔三角洲发育一大型重力滑动构造。自非洲大陆向南大西洋方向,该重力滑动构造可以划分出前缘挤压构造变形区和后缘拉张构造变形区。前缘挤压构造变形,形成褶皱冲断带;后缘拉张构造变形,形成堑垒构造;两者之间的过渡带发育滑脱褶皱。三角洲沉积的时代为始新世—第四纪,地层剖面自下而上依次是海相页岩(Akata组)、近海三角洲相砂岩—页岩互层(Agbada组)和陆相冲积砂岩(Benin组)。3个岩石地层单元都是穿时的,向大洋方向变新。重力滑动构造的主滑脱面位于Akata海相页岩中。根据生长地层、不整合以及卷入变形的地层时代,重力滑动构造起始于约12 Ma,伴生有广泛发育的泥构造。重力滑动构造的形成可能与新生代喀麦隆火山带(Cameroon volcanic line)的火山活动有一定的关系。     

辽宁海城地区辽河群底部大型韧性滑脱带的构造演化

通过对辽宁海城地区赵家堡子－马风－什司县一带早元古宙辽河群底部地层和变质深成侵入体的详细构造研究，确认了辽河群底部与太古宙之间大型韧性滑脱带的存在。卷入滑脱带的地质体有辽河群底部浪子山岩组和早元古宙变质深成侵入体。滑脱带的构造演化可划分为：①吕梁运动早期沿太古宙与早元古宙接触带部位发生大规模拉伸顺层滑脱变形作用；②拉伸滑脱变形中晚期早元古宙深成侵入体沿滑脱带顺层同构造就位；③吕梁运动晚期滑脱带的收缩变形作用三大阶段。     

塔北地区变形样式及其分布规律

塔北地区包括库车前陆盆地和塔北前陆克拉通地区两大变形带，在库车前陆盆地，垂向上，主要受滑脱层发育及其展布、构造地层组合及岩层埋深等因素控制，深层一般为被动顶板双冲构造及断变褶皱，中层三角带、冲起构造，浅层为断展，滑脱及底辟褶皱；横向上，与挤压应力大小、地层岩石力学性质、滑脱层发育程度等相关，自造山带前缘向前陆克拉通方向，褶皱一般由紧闭，不对称或倒转变为平缓，开阔，并由断变，断展褶皱变为滑脱褶皱；变     

滑脱层在挤压构造变形中的作用——来自构造物理模拟实验的证据

为了研究滑脱层在挤压构造变形中的作用,通过物理模拟实验,观测了两种构造挤压方式(即单向挤压、双向挤压)作用下不同时期及不同部位地层的构造形成及其晚期演化特征.实验结果表明:①在滑脱层存在的地质条件下,地质体自下而上可以划分为三个构造变形单元,即"上构造层、滑脱层、下构造层".②构造变形过程可以划分为3个时期,在变形初期...     

呼图壁背斜构造模型和成因机制

呼图壁背斜位于准噶尔盆地南缘褶皱—冲断带的北部，属于天山向准噶尔盆地下方逆冲带的最前缘。基于全新的高精度三维地震资料，本文揭示了呼图壁背斜具有上下分层变形的特点，背斜发育双层滑脱的构造形态，浅层主要以古近系紫泥泉子组的石膏质泥岩为滑脱面，与上覆的古近系和新近系地层产生滑脱背斜；深层主要以侏罗系的八道湾组和西山窑组的煤层为区域性的滑脱面，产生侏罗系和上覆地层的断背斜构造，深浅层滑脱叠置，总缩短量达1 210 m。受二叠系隆凹构造格局的影响，石炭—二叠系古凸起对新生界的变形具有定形、定位的作用。利用ADS法定量分析和研究表明呼图壁背斜的形成经历了前期弱挤压构造运动，发育时间在新近纪，约23 Ma，后期为强烈的挤压构造运动，时间在7 Ma左右，呼图壁背斜的发育与南缘天山的期次隆起具有很好的响应。     

塔里木盆地北部库车地区秋里塔格构造带地层结构及其对构造变形的制约

本文利用露头、钻井、航空照片和地震反射等资料,通过地层对比与构造分析等综合研究手段,分段解剖了秋里塔格构造带地层结构与构造变形特征,进而探讨了地层结构对构造变形和油气成藏的影响。秋里塔格构造带东、西地层结构有显著差异,发育几套非能干层,如膏盐岩和煤系等塑性地层,其发育层位和展布范围侧向变化迅速,形成多个滑脱面,将中新生代变形地层分为深、浅两套变形序列。受滑脱面侧向变化的控制,深、浅变形序列卷入地层及其构造样式和类型发生相应的转变。此外,受不同的地层结构和构造演化背景的控制,该带东、西形成两种截然不同的油气成藏类型,即近源垂向运移型和远源侧向运移型。     

川西地区构造滑脱层岩石力学特征及构造变形意义

通过川西地区岩石样品单轴抗压强度测试和三轴抗压强度测试,认为岩石抗压强度与岩石密度具正相关关系。早期地层常具有较大的岩石抗压强度、弹性模量、泊松比,粘聚力亦具有类似变化趋势。构造滑脱层应具有相对较小的单轴抗压强度、较小的弹性模量和较小的泊松比。该区从上侏罗统至中奥陶统各地层中发育多套滑脱层,即上侏罗统蓬莱镇组、中三叠统雷口坡组、下泥盆统和志留系等。滑脱层在构造变形中多表现为各逆冲断裂下部汇聚或尖灭消失的构造软弱带,且滑脱层上部层位构造变形强度较大,多形成密集分布的逆冲断裂带,而滑脱层下伏区域构造变形微弱,多形成倾角较缓的单斜构造或者宽缓褶皱。     

核废物处置试验场环境地质研究综述

介绍了国外核废物处理试验场有关环境地质研究现状与进展。据核废物的放射性不同，目前或未来处置的方式不一样：中－低放射性废物（ＩＬＷ－ＬＬＷ）一般采用浅层处置，多置于粘土层或沉积岩层中；高放射性废物（ＨＬＷ）一般通过竖井或平巷处置于深部的花岗岩或岩盐中。根据母岩的类别不同，本文分花岗岩、岩盐、粘土及其它四部分，对不同的试验场的研究计划、内容、方法、进展等进行了评述。     

山西沁源隐伏铝土矿综合物探调查应用效果

铝土矿床受控于奥陶系灰岩构成的古地貌,与成矿盆地内赋矿地层石炭系本溪组的厚度正相关,盆地斜坡带、洼地、凹槽及岩溶漏斗地段是铝土矿富集有利部位。奥陶系灰岩与上覆地层有较明显的密度和电性差异,铝土矿体与围岩也存在密度差。借助于可控源音频大地电磁测深法(CSAMT)及钻孔的标定,利用重力异常可以了解研究区的构造格架和奥陶系灰岩基底的起伏变化,确定局部高密度体的赋存状况及性质,并大致确定其埋深。在山西沁源成矿远景区中深部隐伏铝土矿调查中,采用1∶2.5万重力和CSAMT法直接与间接找矿相结合的方法取得了较好的应用效果,为钻孔布设提供了依据。     

Late tortonian—lower messinian (miocene) palaeogeography of SE Sicily: information from two new formations of the sorting group

A thick volcanoclastic, biohermal and lagoonal sequence of strata succeeds the Siracusa Limestone Member (Monti Climiti Formation) of SE Sicily. This overlying sequence may be divided into two new formations on the basis of lithostratigraphy, petrology and palaeontology. The older formation, here named the Carlentini Formation, is predominantly a thick volcanoclastic sequence but with two intervening carbonate horizons. Faunas are rare within the volcanic strata but may be abundant and associated with corals and patch-reefs within the two carbonate levels.The younger formation, here named the Monte Carrubba Formation, is almost exclusively composed of oolitic grainstones and lagoonal wackestones. Peritidal carbonates are developed in the northeast of the area. Faunas are frequently of low diversity. Euryhaline mollusc associations are dominant, although Pecten vigolenesis occurs in the lower beds.Collectively the new formations span the late Tortonian—lower Messinian time interval and may be correlated with the Calcare di Base of the main sicilian basin to the west.The palaeoenvironmental reconstruction suggests that both formations were deposited around the SW margins to a low island or landmass lying to the north of the Hyblean region.     

Lithochemical typification of Early Precambrian ferruginous-siliceous formations in the East European Craton

The first comparative paleolithochemical characteristics of Early Precambrian ferruginous-siliceous formations of the East European Craton confined to four stratigraphic levels—Lower Archean, Upper Archean (Lopian), Lower Karelian, and Upper Karelian—are presented. Using the MINLITH method and software package for lithochemical calculations, the possible primary composition of metasedimentary rocks is reconstructed and paleogeographic settings of sedimentation are suggested. It is shown that different age formations represented initially lithogenetic groups with different compositions and quantitative relationships between the major types of sedimentary rocks with gradual transitions and genetic affinity. They accumulated in paleotectonic and facies settings that were specific for each stage of iron ore sedimentation, resulting in the development of four genetic (Bug, Algoma, Okolovo, and Lake Superior) types of ferruginous-siliceous formations.     

Combined climatic and geological forcings on the spatio-temporal variability of piezometric levels in the chalk aquifer of Upper Normandy (France) at pluridecennal scale

The temporal variability of water-level fluctuations in the chalk aquifer of Upper Normandy, France is constrained by natural climate fluctuations and is closely linked to the regional geological patterns. The chalk plateaus are covered with 5–50 m thick semi-permeable surficial formations; the thickness of the underlying chalk aquifer varies from 50 to 300 m. The relationship among climate oscillations, piezometric levels, and geologic structure were investigated by correlation, Fourier spectral, and continuous wavelet analyses of selected piezometric time-series data. Analysis focused on two piezometers located on the uplifted side of a major fault and two piezometers on the downthrown side. After generalization to other piezometers in the region, it was deduced that, in the downthrown compartments, a substantial aquifer and surficial formations thickness would imply a strong attenuation of annual variability, while multi-year variability is clearly expressed. Conversely, in the uplifted compartments, a thin layer of surficial formations and small thickness of the chalk authorizes strong variations on the annual mode with respect to the contribution of long-term climatic oscillations (multi-year variability). The results then demonstrated—and proposed a spatial determination of—the differential influence of geological patterns on the filtering of climate-induced oscillations in piezometric variability.     

Silicified Woods Consist with Malachite,Azurite, and Hematite in the Middle Eocene Çekerek Formation,Tokat—Turkey

Lithology and Mineral Resources - In the vicinity of Yücepinar Village of Zile district of Tokat province, there are silicified wood formations in agglomerate levels in the Çekerek...     

Diffusion-driven transport in clayrock formations

Clay mineral-rich sedimentary formations are currently under investigation to evaluate their potential use as host formations for installation of deep underground disposal facilities for radioactive waste (e.g. Boom Clay (BE), Opalinus Clay (CH), Callovo–Oxfordian argillite (FR)). The ultimate safety of the corresponding repository concepts depends largely on the capacity of the host formation to limit the flux towards the biosphere of radionuclides (RN) contained in the waste to acceptably low levels. Data for diffusion-driven transfer in these formations shows extreme differences in the measured or modelled behaviour for various radionuclides, e.g. between halogen RN (³⁶Cl, ¹²⁹I) and actinides (^238,235U, ²³⁷Np, ²³²Th, etc.), which result from major differences between RN of the effects on transport of two phenomena: diffusion and sorption. This paper describes recent research aimed at improving understanding of these two phenomena, focusing on the results of studies carried out during the EC Funmig IP on clayrocks from the above three formations and from the Boda formation (HU).     

Origin of water salinity in a lake and coastal aquifer system

The studied area is in the Algerian Northeast. A number of interacting factors at the site are able to modify salinity. The main influences are: (1) The lithology, (2) Fedzara Lake, (3) marine waters, and (4) a prolonged drought. (1) The lithology is very clearly delineated by the outcrop of metamorphic formations (gneiss, marbles, micaschists, and quartzites) and sedimentary formations (limestones, clay, sandstones, and sands). All these formations can influence the chemical composition of waters. (2) Fedzara Lake evacuates its salted waters via the Wadi Meboudja, which connects with the Wadi Seybouse and the phreatic surface. These lake waters might induce changes in salinity. (3) The marine waters represent the third source of salinity change. Over-pumping of water from wells and drillings can cause an imbalance to the fresh–salted water interface. (4) The effects of a local prolonged drought of more than 10 years may increase water salinity. Over-pumping to augment water supply generates a fall in water levels and the drier atmosphere increases evapotranspiration. Both may contribute to increased salinity. Results of water analysis were used to observe the evolution of these various factors.     

The beating heart of Earth's climate revealed: caves5 coral reefs and coastlines in the Balearic Islands

Studies of cave formations, an exhumed Miocene reef platform and drowned Pleistocene coastlines in the Balearic Islands show how sea levels are constantly changing. Could even more exhaustive studies of this sort help us predict future climates'?